1. Technical Field
The present disclosure relates to a backlight driver, a display apparatus having the same and a method of driving the backlight. More particularly, the present disclosure relates to a backlight driver capable of improving the response speed of the backlight and stabilizing the brightness, a display apparatus having the backlight driver and a method of driving the backlight.
2. Discussion of Related Art
In general, a liquid crystal display (LCD) includes an LCD panel that is illuminated by a backlight. A cold cathode fluorescent lamp (CCFL) is commonly employed as the LCD backlight.
Many applications require dimming capabilities, for example, to improve the contrast ratio of the display device and increase battery life. A dimming method has been utilized that controls the brightness of the backlight to increase a contrast ratio of the LCD or to decrease electric power consumption by the backlight. The dimming method can be classified into a pulse width modulation (PWM) control method and a current control method.
In dimming by a PWM control method, the CCFL is repeatedly turned on and off in accordance with the duty ratio of the PWM signal, thereby causing the CCFL brightness to vary. That is, the PWM control method involves switching the CCFL on and off at a regular interval to adjust the brightness of the backlight by changing the duty ratio.
Tube current is the current flowing through the CCFL tube after the tube has been lit. The CCFL brightness is directly proportional to the tube current. The current control method controls a voltage level applied to the CCFL to vary the tube current of the CCFL, thereby adjusting the brightness of the backlight. However, since the current control method is not designed to control the brightness in a low current range, the PWM control method has been mainly used for illumination control of the CCFL of the LCD backlight.
In the PWM control method, however, the response speed of the backlight decreases in the range of a low duty ratio of the PWM signal while the backlight is being dimmed, and a brightness blurring phenomenon can occur, thereby deteriorating the image display quality on the LCD.